Wireless sensors are used in a variety of applications such as reading gas meters, monitoring temperatures, etc. These wireless sensors are often placed in locations where they cannot be plugged in to a wired power source and therefore must rely on battery power for long periods of time. To conserve battery power, these devices typically go into a low-power mode between measurements and communications.
Often, these wireless sensors communicate with an application server via an access point (e.g., a Wi-Fi router). An access point is a device that allows wireless devices, such as wireless sensors, to connect to a wired network, such as the Internet. Typically, each time the application server sends data to a wireless sensor, the data are first buffered by the associated access point until the wireless device comes out of low-power mode.
When a wireless station comes out of low-power mode, the access point lets the wireless station know that the access point has buffered data for that wireless station. Typically, the access point does this by broadcasting a unique identifier associated with each such wireless station. However, if large number of wireless devices (e.g., thousands of sensors deployed in a building) require frequent updates, the list of unique identifiers is long. As a result, each wireless device may need to stay awake for extended periods of time, thereby reducing battery life.